In this engineering activity (page 5 of PDF), young learners investigate how materials and design contribute to the strength of a structure, particularly walls. Learners use different materials to construct "walls" and then test the strength of each by setting up a ramp near the wall and releasing a car from the top of the ramp. Learners also watch a video clip and develop a fair test to compare the strength of the different walls they have constructed. This activity is part of the Curious George "Under Construction" lesson plan and related to the show Curious George on PBS, specifically the episode "Keep Out Cows." The lesson plan includes several activities that explore building engineering. Activities are connected to fiction and non-fiction books and include family extension projects.